Cost-benefit analysis of retrofitting attic-integrated switchable insulation systems of existing US residential buildings

This study evaluates the cost-benefit of retrofitting attic using switchable insulation systems (SISs) for existing US residential buildings. For the retrofit analysis, the SIS insulation, is operated using 2-step temperature based controls and its energy performance is compared to that achieved by static code-required insulation installed in attics of detached homes located in 44 US locations. The analysis results show significant correlations between source heating/cooling energy savings and degree-days as well as sol-air temperatures used as climate indicators for the US locations. In addition, it is found that the potential energy savings achieved by attic-integrated SIS insulation retrofit vary widely by climate ranging from 14 kWh/m² to 51 kWh/m². For all US locations, the analysis indicates that deploying the attic-integrated SIS can provide higher cost savings compared to static high R-value insulation. Based on a breakeven cost analysis, the annual energy cost savings when replacing the existing insulation with attic-integrated SIS range from $0.05/m² to $1.57/m² depending on the climate. The additional cost for the deployment of SIS insulation can be on average 55% more than the current static insulation US prices to ensure its cost-effectiveness as a retrofit measure for attics of US residential buildings.